Thermistor device has been widely used in current limiting circuit, including motor starting circuit in a refrigeration device such as a refrigerator. After being used for long time, the physical structure of the prior art PTC device may deteriorate, creating abnormal heat inside the device and breaking the PTC element into fragments. Since the fragments may still be connected with the terminal, issues such as arc discharging, overheating, over current, etc. may occur.
U.S. Pat. No. 6,172,593 assigned to Murata Manufacturing Co., Ltd. Introduces an electronic device with two spring contact parts and two non-conductive contact parts. During operation period, the four contact parts contact with PTC, and the two spring contact parts are welded to the left and right terminals respectively. On one hand, the material closely contact with PTC (non-conductive contact parts) need to be resistant to high temperature and thus is relative expensive. On the other hand, in the case that PTC is broken without disconnecting current, the fragment of PTC still electrically connected with the terminals, creating arc discharging and over-heating.
CN patent application CN102347123 filed by Sensata Technologies Massachusetts, Inc. introduces a thermistor device with three elastic support and a pair of insulated offset posts, wherein two elastic support is welded to a terminal and a third elastic support is welded to another terminal. Said pair of offset posts are spaced from the thermistor element. Since the posts do not contact with the PTC element, it does not need expensive material resistant to high-temperature. However, in the case that the thermistor is broken without disconnecting current, the fragment of the thermistor still electrically connected with the terminals, creating arc discharging and overheating.
Thus, current thermistor device may not be able to reliably eliminate the issues of arc discharging and overheating in a failure broken state.